In recent years, hybrid vehicles have become widespread as environmentally-friendly vehicles. As a power source for driving wheels, hybrid vehicles have a motor which is driven by electric power supplied from a battery or a generator, in addition to an engine fueled by gasoline, diesel fuel, or the like.
In some of these hybrid vehicles, a DC voltage supplied from a battery is boosted by a DC/DC converter (hereinafter referred to as a “converter” where appropriate), which is a voltage converter, and the boosted voltage is supplied to an inverter where the DC voltage is converted to an AC voltage and applied to an AC synchronizing motor.
Further, in order to maintain the state of charge (SOC) of a battery within a predetermined appropriate range, control is performed on the electric power generated by a generator from a power of the engine and braking force of the vehicle and control is performed on the electric power consumed by a traction motor of the vehicle.
By including a traction motor in combination with an engine as a power source, such a hybrid vehicle achieves a more fuel efficient drive than that of a vehicle that includes an engine alone as a power source. However, there is still a need to achieve even higher fuel efficiency and energy saving by, for example, enhancing operational efficiency of the motor and engine. Therefore, it has been proposed to provide a switch or the like for instructing a vehicle controller to perform a fuel efficient drive when a user turns ON the switch to give a priority to fuel efficiency rather than to vehicle driving performance. Such a switch is called an “eco-mode switch” or simply “eco switch.”
For example, JP 2007-159214 A describes an electric vehicle equipped with an eco switch. It is described that when the eco switch is turned ON by a user operation, a boosting operation of a converter is stopped to thereby eliminate a switching loss at the converter in order to enhance fuel efficiency.